There is considerable evidence favoring our notion that calcium plays a central role in the initiation of vision. A definitive test for this hypothesis is a measurement of transient light stimulated calcium activity changes in the visual receptor cell. The properties of a calcium sensitive dye, dichlorophosphonazo III, have been studied and found suitable for this purpose. A rapid multi-wavelength spectrometer was built to measure ionic activity changes reported by dichlorophosphonazo III in thin tissues like the retina. Isolated retinas can function as light detectors but cannot regenerate visual pigments. We have invented a method using liposomes to permit pigment regeneration in such retinas. This technique is applicable to general practice of introducing large amounts of water insoluble chemicals into live tissues. Using this method, we are studying the biochemical pathway of retinol in the visual process and discovered among other things the retinol oxidation enzyme in the retina is specific for a given stereoisomer. BIBLIOGRAPHIC REFERENCES: Weinstein, S., Yoshikami, S., Henbart, P., Blumenthal, R., and Hagins, W.A.: Liposome-cell interaction: Transfer and intercellular release of a trapped fluorescent marker. Science 195: 489-492, 1977.